A surveillance system usually includes one or more video cameras, video data storage (video server, video archiving system, or video recorder), and an operator's workplace. Streaming video data is received from the video cameras, recorded in video data storage and displayed at an operator's workplace.
Methods of video data search are an integral part of almost any video surveillance system. Modern video data storage allows to quickly searching and play recorded video fragments upon a user request. This random (direct) access to video data is implemented by means of video data marking or indexing. An index is a lookup table, connecting marks with addresses of the corresponding video data. The index significantly reduces access time to video data recorded in storage for further processing by the user or the computer.
A temporal index associates the temporal scale to video data, i.e. it allows the storage of quick searches of video data based on a specified date and time.
An event index contains a table of events and allows the storage of quick searches of video data based on a specified event such as signals of a motion detector or other sensors connected to the video surveillance system.
Video analytics, i.e. video analysis tools, based on vision algorithms, can be a source of events for generating the index. For example, video analytics allow defining such events as the motion of a person in a given direction and the appearance or disappearance of an object.
The index can contain additional information regarding an object that is recognized by video analytics for further search of video data. For example, the index can contain vehicle registration plate information, a person's height, a color of clothing or facial features.
As a rule, the indices are built in real time on an ongoing basis; they consist of video data sent into storage from surveillance cameras. The indices are subsequently used in the processing of user requests for information in video data storage.
Online video storage services like YouTube (http://youtube.com/) and Vimeo (http://vimeo.com/) also use various indices, e.g. indices based on video publishers and keywords. These services allow access to portions of video data by means of a hyperlink and playback of the video using browsers or mobile devices.
Online video surveillance services like DropCam (http://dropcam.com/) and iVideon (http://ivideon.com/) allow the reception of video data from users' surveillance cameras and the transmission of this data to browsers or mobile devices.